The agency must provide Medicaid to individuals who—

(a) Meet all current requirements for Medicaid eligibility except the criteria for blindness or disability;

(b) Were eligible for Medicaid in December 1973 as blind or disabled individuals, whether or not they were receiving cash assistance in December 1973; and

(c) For each consecutive month after December 1973, continue to meet the criteria for blindness or disability and the other conditions of eligibility used under the Medicaid plan in December 1973.